Mold for centrifugal castings



July 14, 1942. H. 'PROJAHN EAL l 2,289,681

MOLD FOR CENTRIFUGAL CASTINGS Filed Jan. l0, 1940 Y l v N A" Inv/@Mors Patented July 14, 194.2

i UNnEDsTATEs PATENT o1-Fica ,y

l. MOLD Fon cnNTmFUGAL cosmos Heinrich Proiahn and Albrecht von lankenberg und Ludwigsdort, Gelsenkirchen, Germany. assignors to United States Pipe and Foundry Company, Burlington, N. J., a corporation of New Jersey Application January 1o, 1940, serial No. naiss In Germany December 7, 1938 5 Claims. (Cl. 22-65) Our invention relates to the construction and make up of molds adapted for use in the centrifugal casting of iron or steel tubes such as pipes. Our mold construction involves -a permanent metallic outer wall, a substantial part of which is of approximately rcylindrical form and an impermanent inner lining of substantial thickness made u'p of refractory granular material adapted to keep the casting made in the mold at asubstantial distance from the metallic mold wall and thereby minimize the chilling eiect of the metal wail during the pouring and hardening of the molten metal. A prime object4 of our invention is to provide both the lining and the metal wall structure with multitudinous intercommunicating interstilces whereby air or other gases and vapors can escape freely in a radial direction from any point in the lining in which they exist or may be created, thereby greatly decreasing the liability of a defective casting being produced by undue vpressure of gases .or vapors during the period when the outer wallof the casting is in fluid or in partly fluid condition.

The outer metallicvwall of our mold, or at leastr such portion of its length as corresponds with the cylindrical portion of the castingto be produced', is made up of a metal structure provided with a multiplicity ci intercommunicating interstices affording free radial passage for gases and vapors existing or generated in' thev mold lining during the casting operation; k'The lining portion of the moldshould also be'of such a structure as to provide intercommunicating interstices forming ymultitudinous channels kforthe escapeof gasesv and vapors in a generallyradialdirection through thelining during the ecastingloperation.

Suchzmetallic structures as are adapted vfor our purposesgingmaking theouter wall `are known and consist ofiritted or sintered metal powder,`

metal chipsor other small metallic particles,` or what are' known as metal Sponges;` So far as 4the make up ofthe lining is concerned, that' binder may be used in such ouantity as to coat at least the inner portion of the lining and cause adherence of contacting points vof the granules without closing the intercommunicating intera,l stices, but care is taken that the binder should not be used in such quantity as to practically embed the granules in the' binder and form `a lining structure having no,` or very greatlyv re-` duced, permeability to gases in a radial direction. Where considerable structural strength in the lining is considered advisable the granules of l refractory material used in its formation may be provided with a thin coating of a .substance which, under the conditions existing during the casting operation, will so fusev or be otherwisel affected as to form a union of the coating of contacting grains at their points of contact thus y forming an eective binder for thegrains without seriously contracting the intercommunicating interstices between the grains. We would mention as substances or compounds adapted for such usages sillcateswith sodium or potassium, bentonite, sulphite solution, pot-ilour, oil-binder, tar-binder and so on,but obviously ay substance or compound coating the grains and having the property of causing adhesion between ythe contacting points of grains may be used with advantage.

For practical purposes we have found that, in

most cases, the refractory granules making up the lining will be sufllciently stabilised if only their inner layer is provided with coatings adapted to bring about adhesion between contacting best adapted for the purposes we have in view a lining l,inode-of refractory granules "contacting with each other preponderantly only atlpoints andV largely stabilised, positionedjand .held in position on the metallic wallof` the Vmold by centrifugal force` generated bythe revolution of the mold at 'suiliciently high speeds, first, to help i in the distribution f ofi the' lining material intoA proper form'v and"then` to impart suiliclent stau bility tothe liningias-tol counteract the washing eiect ofthe molten metal during the pouring operation. For practical f purposes, however, 'a

points. and that the binder can be satisfactorily appliedV to the inner layer of the lining in the form of a liquid sprayv which will preferably be `used in quantity suilicient only to insure that the contacting particles on this inner layer :are made adherent to each other without; entirely closing thev intercommunicating interstices of this layer. Obviously however the closureof intercommunieating interstices at or immediately beneath the l interiorsurfvace of the lining would not be serlously detrimental `il? the great body of the lining has its granules suiliciently spaced tto afford a free ilow of gases and vapors radially.

Experiments have shown that considerable stability can be imparted to the inside layer of y the lining .by applying to the inside face of the lining a facing, for example, of iine graphite black. 'Such a facing may be built up of metallic substances, such as aluminum powder, 4or metallic oxides, such as aluminum oxide. Magnesia can also be used as a facing. It is particularly advisable to use emulsions or colloidal solutions oi' such materials in Water-glass or even in oleaginous binding agents, or to incorporate or apply boric acid or similar substances behaving like glass under not too great heat in or on the innermost layer coming into contact with duction of the critical speed of rotation is alsoI rendered possible.

Such a lining as we have described for use in metallic molds of the ordinary kind and having no radial permeability to gases, has been described and claimed in United States patent applications by Proiahn, Serial Number 240,495. filed -November 15, 1938, andl Serial Number 240,643, filed November 16, 1938, and is only intended to be covered in this application when used in connection with radiallypermeable metallic molds such as described herein.

We are aware that prior to our invention molds have been constructed, :in part at least, from agglomerated metallic powders, chips or the like, -so as torbe permeable to gases, and that metal has been cast against the inner surface of such molds but without the use of a lining. We are also aware that prior to our invention solid metallic walled molds have beendrilled through at numerous points to provide for a radial flow of gases through the wall of themold and that such molds have been lined with the ordinary rammed lining in common use. But such drilled molds would not be practical with such comparatively loosely compacted linings as we have @Y described, as lining particles would escape through the drilled holes or, in the alternative, tend to plug them up and moreover would not provide, as do the structures we have described, for the free radial flow of gases through the wall in all parts of the wall structure. v

To diminish the liability'of lining particles escaping into the inner interstices. in the mold vwall we consider it advisable in the manufacture of a mold to provide that the area of the interstices should be less than that of the average diameter of the vgranules used in the make up oi the lining, and preferably we so 'construct the mold wallthat the areas of the spaces at the in v side of the'mold wall should be even smaller than the areas more remote from the inner face of the mold wall. Still further to diminish the liability of particles of the lining escaping into the interstices of the wall it is advantageous to apply to the inner face of the moldwall a wire screen having a mesh which will retain liningr particles of *a size smaller'than the averagesize `of the granules making up the lining.

' Referring to th'e drawing which forms a part lof this specification, Figure 1 is an elevation of a pipe casting apparatusincluding a mold, indicated at A, mounted for rotation on a longitudinally movable carriage B, supportedon track C, means for imparting reciprocating movement to the carriage being indicated at D and means for rotating the mold indicated at E. F indicates a ladle for the molten metal supported on a pedestal F1. G in-l dicates mechanism fortilting the ladle. H indicatessa trough for feeding molten metal from the ladle to the inside ofthe mold, the trough being supported on the pedestal supporting the and facilitate the v shown in section. J indicating a section through the metallic wall of the mold. K indicating the lining forming the inner wall of the mold, and L indicating a wire mesh located between the metal wall of the mold and the outer wall of the lining. v

The -wire mesh L may or may not be used.

Figure 2 is a view on a larger scale of the makeat M of the casting formed on the inner lining of the mold. This view'also indicates that a binder coating O has been applied to the inn`er layers of the lining, the showing of the outer metallic wall of the mold indicating that it is made up of chips of metal sintered together., so as to provide for intercommunicating 4interstices throughout the ,thickness of the wall. l

Figure 3 is similar to the showing of Fig. 2, ex# cept that the structure of the outer metallic wall is indicated as such as would result from the use of a metallic sponge in the formation of the wall.

Figure 4 is a view generally similar. to Figs. 2 and 3, except that the screen Lis omitted and the metallic outer wall of the mold is shown as of a construction which indicates larger intercommunicating interstices in the outer portion of the wall than in the inner portion.

Figure 5 is a rather diagrammatic elevation on a very large scale of a construction in which the granules forming an inner layer of the lining are indicated as coated with a bindingy agent which forms at points where it contacts with the t coating of adjacent granules a union serving to mately cylindrical bodies of iron and steel, comprising an outer metallic, permanent shell of such construction that its wall throughout its thickness is made up of an aggregation of adherent metallic particles so disposed in the wall as to withstand the stresses due to rotation of the mold and to provide multitudinous intercommunicating interstices affording a free passage for gases or vapors throughout the entire thickness of the wall, andan impermanent lining for said shell made up for the most part of loosely arranged refractory granules used in such quantity as to provide a lining of substantial thickness and so disposed with regard to each other as to provide the lining with multitudinous intercommunicating interstices forming paths for the passage of gases and vapors throughout the greater part of the thickness of the lining structure.

2. A.mold as called for in claim 1, lin which the intercommunicating interstices of the metallicfouter wall are made narrower at and near the inner surface of the metallic wall.

3. A mold ascalled for in claim 1, in which y a cylindrical wire screen of a mesh smaller than the average area of the intercommunicating-interstices formed through the metallic wall where such interstices open through the inner surface of the',wal1 is located between the said metallic wall and the inner lining of the mold. f

4. A mold as called for in claim 1, in which the granules used in the make up of the lining are more or less stabilised by the application to the grains. forming the inner portion of the lining of a binder in sufcient quantity to bring about an adherence between contacting parts of such grains without closing the intercommunieating interstices between said grains.

5. A mold as called for in `claim 1, in which fthe granular-material used in the make up of at least a large portion of the lining is held in place 10 during the make up of the mold lining and during the pouring of the mold by centrifugal force generated during the make up 'and pouring of the mold by its rotation at suicient speeds to impart necessary stability to the granules used in the make up of the lining.

HEINRICH PROJAHN. AIBRECHT VON FRANKENBERG UND LUDWIGSDORF. 

